G O’Sullivan1, S Chaturvedi2,3
1Townsville University Hospital, Townsville, Australia, 2Department of Paediatrics, Royal Darwin Hospital, Darwin, Australia, 3Menzies School of Health Research, Charles Darwin University, Darwin, Australia
Background: There have been multiple recent articles and case reports discussing a de novo interstitial deletion of 4q21. A typical phenotype including macrocephaly, growth and developmental delay, distinctive facial features and hypotonia has been described. The involvement of the PKD2 gene in this syndrome has not been discussed in detail in previous reports.
Case Report: We report an 11-year-old boy who was initially referred to a paediatrician with learning difficulties and speech delay who diagnosed him with autism spectrum disorder. He was macrocephalic and had subtle dysmorphic features. He was one of two children of non-consanguineous parents. As part of his work up, a microarray was sent which revealed a 5.5Mb interstitial deletion at chromosome 4q21.23-q22.1 involving the PKD2 gene. He also had an MRI Brain which revealed small pineal cyst. His initial kidney ultrasound was reported as normal. He was subsequently referred to a paediatric nephrologist at 17 years of age. He was noted to be macrocephalic and had dysmorphic features consistent with the previously reported phenotype including frontal bossing, short philtrum, hypertelorism and small hands and feet. He was obese with weight 114 kgs (99th centile) and height 175.2 cm (38th centile). He was normotensive. He had an abdominal ultrasound which revealed bilateral multiple renal cysts in keeping with autosomal dominant polycystic disease (ADPKD). Blood tests revealed chronic kidney disease (CKD) stage 1 (eGFR 92ml/min per 1.73m2 x CKD-EPI equation). He had no proteinuria or haematuria.
Conclusion: This report adds to the phenotypic spectrum of this contiguous gene deletion syndrome. It highlights the importance of potential kidney involvement in the form of ADPKD and the need for regular surveillance of these patients.
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